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- Title
Intraseasonal Variability of the North Equatorial Current Bifurcation Off the Philippines.
- Authors
Zhou, Hui; Liu, Xueqi; Li, Ruixiang; Wang, Yonggang; Yang, Guang
- Abstract
Characteristics of the intraseasonal variability (ISV) of the North Equatorial Current bifurcation latitude (NBL) are analyzed by using both observations and reanalysis data. The maximum amplitude of the ISV of the NBL can reach about 6° of latitude, which almost triples its annual excursion. The NBL shows a broad spectral peak around 50–140 days with the highest peak occurring around 73 days. Both the Madden‐Julian oscillation and mesoscale eddies have a significant impact on its ISV. A case study for a cyclonic eddy indicates that it can transport about 1.5 Sv (1 Sv–106 m3 s−1) waters to the NBL, and the bifurcation shifts northward with an amplitude of about 8° of latitude in 1 month. Meanwhile, the influence of mesoscale eddies on the ISV of the NBL is highly modulated by the interannual variations of the eddy field. Active eddy activities associated with enhanced barotropic and baroclinic instabilities show a large influence on the NBL. The eddy kinetic energy level around the NBL showed a quite diverse character for the 1997–1998 and the 2015–2016 extreme El Niños, with the latter being double or triple that of the former due to the much stronger vertical and horizontal shears. Given the significant impact on the NBL by the individual eddies and the unevenly distributed cyclonic and anticyclonic eddies around the NBL, the effect of mesoscale eddies on the bifurcation latitude may not cancel each other on seasonal or interannual time scales. Plain Language Summary: The North Equatorial Current bifurcation latitude (NBL) determines the mass, heat, and salt partition between the Kuroshio and the Mindanao Current. Variations in the NBL exert profound effects on the tropical Pacific climate and need to be better understood. This study identifies significant intraseasonal variability (ISV) of the NBL with the maximum amplitude reaching about 6° of latitude, which almost triples its annual excursion. Both the Madden‐Julian oscillation and mesoscale eddies have a significant impact on its ISV. A case study for a cyclonic eddy indicates that it can transport about 1.5 Sv waters to the NBL and perturbs the bifurcation significantly. Meanwhile, the influence of mesoscale eddies on the ISV of the NBL is highly modulated by the interannual variations of the eddy field, and active eddy activities associated with enhanced vertical and horizontal shears show a large influence on the NBL. Given the significant impact on the NBL by individual eddy and unevenly distributed cyclonic and anticyclonic eddies around the NBL, the effect of mesoscale eddies on the bifurcation latitude may not cancel each other on seasonal or interannual time scales. Key Points: The North Equatorial Current bifurcation latitude shows significant intraseasonal variability (ISV) with the maximum amplitude tripling its annual excursionBoth the Madden‐Julian oscillation and mesoscale eddies have a significant impact on its ISVA case study for a cyclonic eddy indicates that it can transport about 1.5 Sv waters to the NBL and perturb the bifurcation significantly
- Subjects
PHILIPPINES; PACIFIC Ocean; EQUATORIAL currents; MESOSCALE eddies; CLIMATE change
- Publication
Journal of Geophysical Research. Oceans, 2021, Vol 126, Issue 11, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2021JC017646